1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to systems and methods for the simultaneous execution of operations. In particular, the present invention relates to the simultaneous operations of assembling, dismantling, and maintaining equipment being installed by an offshore oil rig.
2. Description of the Related Art
Oil production at sea requires the use of drilling rigs and completion rigs. These drilling rigs and the completion rigs are used during many different phases in the operation of an offshore oil rig. These phases range from the drilling of wells to the lowering of subsea equipment, such as wet Christmas trees, pumping modules, and other devices.
The operation of these rigs employs a large quantity of manpower and has high costs. These rigs have systems for lifting loads, handling and moving loads, rotating loads, generating and transmitting energy, circulating fluids, ensuring well safety, and monitoring.
The systems for lifting loads, moving loads, and rotating loads are the principal systems used for assembling, dismantling, and maintaining equipment, tools, and accessories and for lowering equipment to or recovering it from the well or the sea bottom. These equipment, tools, and accessories may be used, for example, for the connection, disconnection, and assembly of tubes used to pump oil out of the well.
A system to lift and lower loads comprises a suspension tower, or derrick, and tools for suspending the load. A load handling and movement system (drawworks) comprises a group of fixed and mobile pulleys, and tools for moving loads; and a system for rotating loads comprises a rotary table, located below the suspension tower, and other tools such as transmission components (the Kelly) and the drive swivel.
Rigs also usually have an area open to the sea, similar to a swimming pool, known as the “moon pool”, just below the rotary table, where large-scale equipment is assembled and dismantled.
Operations such as assembling, dismantling, and maintaining large equipment, and the lowering of tubes and installation of equipment are carried out using the derrick and the rotary table. Since there is normally only one derrick per oil rig, the above operations have to be carried out sequentially, and simultaneous execution of two or more operations is not possible. This increases the time and cost of drilling operations, as well as leaving part of the manpower unoccupied.
U.S. Pat. No. 4,819,730 describes one attempt at solving the above problem. Specifically, U.S. Pat. No. 4,819,730 uses a rig with two towers to make simultaneous operations possible. However, application of this invention is limited to new rigs, built with two towers, which have a higher construction cost. In rigs having only one derrick, the limitations of carrying out operations sequentially remain.